An opioid for use to reduce and/or treat drug addiction

ABSTRACT

having the IUPAC name of (−)3-((S)-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)(3-thienyl)methyl)phenol, or pharmaceutically acceptable esters or salts thereof, wherein the compound has activity on the mu, delta and kappa opioid receptors thereby providing added analgesia with an improved therapeutic index and reduced risk of respiratory depression.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/492,232, filed on Apr. 30, 2017, the contents of which are herebyincorporated by reference herein for all purposes.

BACKGROUND OF THE INVENTION Technical Field

The present invention relates to an essentially enantiomerically purediarylmethylpiperazine compound having utility as an agonist at theprincipal opioid receptors: mu, delta and kappa, to be used as atherapeutic agent having utility in combating/treating drug addictionand reducing dependence or tolerance on a dependence-inducing opiatedrug.

Related Art

Substance addiction is a serious public health problem throughout theworld. Heroin and other opioids, including prescription painkillers, arewidely abused and account for a large percentage of illicit drug use.Opioid use is also linked to approximately 50% of violent crimes in theUnited States and costs the U.S. economy billions of dollars per year.

Opioids such as morphine and fentanyl are the mainstay of treatment forchronic moderate-to-severe pain associated mainly with cancer, backinjury (˜38 million) or osteoarthritis (˜17 million).¹ The number ofprescriptions for opioids has risen from around 76 million in 1991 tonearly 207 million in 2013.² The US is the biggest global consumer,accounting for almost 100% of the world consumption of hydrocodone and81% of oxycodone.³

Sadly, the use of opioids has major complications—the risk of death frombreathing cessation and a high probability of dependency. The latter hasbecome an epidemic of abuse and addiction and is regarded by many as anational crisis. It is estimated that between 26.4 and 36 million peopleabuse opioids worldwide.⁴ An estimated 467,000 people in the US areaddicted to heroin, 2.1 million suffered from substance use disordersrelated to prescription opioid pain relievers in 2012⁵—both trends whichare on the rise. The number of unintentional overdose deaths fromprescription pain relievers has soared in the US, more than quadruplingsince 1999. There is also growing evidence to suggest a relationshipbetween increased non-medical use of opioid analgesics and heroin abusein the United States.⁶

Addiction has two components, tolerance and dependence. Tolerance is thedecreased analgesic effectiveness of a drug with continued use. Itsconsequence is the necessity to increase the administered dose of thedrug to maintain the necessary analgesic effect. In the case of theopiates, particularly morphine, the side effects of prolonged use at thevery high doses that sometimes need to be given to sustain analgesia canproduce life threatening results. Tolerance is an effect thus seenduring the course of analgesic administration. By contrast, dependenceis an effect seen only after termination of the repeated administrationof a drug. Upon termination, a drug dependent subject experiences mildto severely harsh and unpleasant withdrawal symptoms. Despite thedesperately recognized need for drugs which reduce tolerance anddependence and produce no unwanted side effects, the search for suchdrugs has, up to the time of this invention, been unsuccessful.

With concerns that current opioid pain medications can be misused,abused or diverted, physicians are increasingly reluctant to prescribeopiates, resulting in under-treatment of patients suffering from chronicpain, a further driver to seek out illegal non-prescription drugs forrelief. Addressing dependency and abuse are high medical andgovernmental priorities. Better education, tighter restrictions onprescription of opioid drugs, and various abuse deterrent (“AD”)technologies are all being pursued. Hitting targets other than theopioid receptors, or receptors involved in downstream signaling are alsonotable. Unfortunately, Trevena's bias ligand approach has beendisappointing as early clinical trial results evidenced typicalopiate-related side effects. The trials on systemic use of TRPV1antagonists have also been disappointing for safety reasons as TRPV1receptors are ubiquitous.

Acute withdrawal from drug dependence is characterized by dramatic andtraumatic symptoms, including sweating, racing heart, palpitations,muscle tension, tightness in the chest, difficulty breathing, tremor,nausea, vomiting, diarrhea, grand mal seizures, heart attacks, strokes,hallucinations and delirium tremens (DTs). Once acute withdrawalsymptoms have subsided, post-acute withdrawal syndrome can last formonths or years. Post-acute withdrawal symptoms include fatigue,depression, lack of motivation, and increased pain sensitivity.

The reality is that no available non-opioid drug is powerful enough tocombat severe pain. However, it would be advantageous to mimic theactivities of endogenous opioid peptides, namely to hit not only themu-subtype of the opioid receptor,⁷⁻⁹ to which morphine and fentanylbind and activate selectively, but also the delta and kappa subtypes.The endogenous opioid system comprises several well recognized opioidpeptides, referred to as endorphins, which collectively activate thethree classical opioid receptor subtypes known as mu, delta and kappa.The pharmacological properties of these opioid receptor classes areclearly differentiated. Commonly prescribed opioids, such as morphineand fentanyl, produce their therapeutic benefit as well as theiraddictive and adverse effects by selectively binding to and activatingthe mu-opioid receptors. Clinicians often reduce the dose of thesemu-opioid receptor agonists to sub-therapeutic levels to avoid thepotentially life-threatening side effect of respiratory depression, andthe more common side effects of nausea, vomiting, hypotension,constipation, and urinary retention.^(7,10) Delta and kappa agonists ontheir own provide a limited advantage in treating pain. Delta agonistspossess some antinociceptive activity of their own¹¹ and importantly,also attenuate the respiratory depression caused by mu agonists¹², whileenhancing their analgesic effect. Kappa receptor agonists may conferincreased analgesia, particularly with visceral pain, and may counteractthe abuse potential of mu agonists¹³⁻¹⁹.

Numerous treatments have been developed in attempts to ameliorate acuteand post-acute withdrawal symptoms. However, in most cases, treatment ofwithdrawal requires use of other addictive substances (e.g., morphine ormethadone). Treatment also requires that the addict attend a clinicdaily for an extended amount of time. Due to the severity and durationof withdrawal symptoms, opioid-addicted patients have a high rate ofrelapse. There is a significant need for effective, non-addictive orless addictive treatment for acute and post-acute opioid withdrawalsymptoms.

SUMMARY OF THE INVENTION

The present invention shows that a ‘mixed’ opioid receptor agonist canprovide effective analgesia yet have a broader therapeutic index forsafety and dramatically reduce dependency and abuse risks. Patients whostill experience pain and are addicted to pain killers such as oxycodonecould substitute the addictive drug with DPI-125 to still conferanalgesia without reinforcing their addiction. In this way, the patientcould be weaned off the addictive drug.

Thus, the present invention relates to a method of reducing and/ortreating drug addiction wherein the method comprises administering to asubject a compound DPI-125 having the structure of formula (I):

having the IUPAC name of(−)3-((S)-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)(3-thienyl)methyl)phenol,or pharmaceutically acceptable esters or salts thereof, wherein thecompound has activity on the mu, delta and kappa opioid receptorsthereby providing potent analgesia with an improved therapeutic indexand reduced risk of respiratory depression with the ability to reducethe euphoric effects associated with mu receptor activation, therebyresulting in reduced abuse potential and hence addiction compared tostandard mu opiate agonists.

Tolerance to the analgesic effects of opioids remains a major impedimentto the use of these drugs in the treatment of pain. Tolerance istypically a decrease in drug effect with repeated or chronic dosing.Thus, in the treatment of chronic pain, a given dose of the pain killerloses its effect and the patient remains in pain despite theadministration of that dose of the opioid. Unfortunately, tolerance tothe analgesic effects of opioids can develop rapidly and requiresincreases in dosage to attain the same analgesic effect. Acute tolerancecan also be seen during time-limited opioid administration, such aspost-operatively or after trauma. The methods of the present inventionare useful in reducing tolerance and/or treating the expression ofopioid tolerance or related disorders. The present invention providesfor a compound having the beneficial effect for: (1) the effectiveinhibition of the development of opioid tolerance; (2) reversal orreduction of tolerance to opioids with primary affinity for the muopioid receptor; (3) reducing opioid dependence; (4) effectiveinhibition of physical dependence; and (5) reducing or inhibition ofaddiction.

Thus, the present invention provides for a method for treating and/orreducing opioid tolerance comprising the step of administering to asubject in need thereof a therapeutically effective amount of thecompound DPI-125 having the structure of formula (I):

having the IUPAC name of(−)3-((S)-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)(3-thienyl)methyl)phenol,or pharmaceutically acceptable esters or salts thereof. The compoundDPI-125 can be administered alone or in combination with another opioid.

The co-administered opioid can be selected from such as, for example,morphine, fentanyl, codeine, thebaine, diacetylmorphine (heroin),dihydrocodeine, hydrocodone, hydromorphone, nicomorphine, oxycodone,oxymorphone, alphamethylfentanyl, alfentanil, sufentanil, remifentanil,carfentanyl, ohmefentanyl, nocaine, pethidine (meperidine),ketobemidone, MPPP, allylprodine, prodine, PEPAP, propoxyphene,dextropropoxyphene, dextromoramide, bezitramide, piritramide, methadone,dipipanone, levo-alphacetylmethadol (LAAM), loperamide (used fordiarrhea, does not cross the blood-brain barrier), diphenoxylate (usedfor diarrhea, does not appreciably cross the blood-brain barrier),pentazocine, phenazocine, buprenorphine, etorphine, butorphanol,nalbuphine, levorphanol, levomethorphan, dezocine, lefetamine, tilidine,and tramadol, propoxyphene, or oxycodone. An opioid also encompasses anynatural or synthetic narcotic antagonist such as nalmefene, naloxone ornaltrexone as well as any natural or synthetic mixed opioidagonist/antagonist such as nalbuphine, butorphanol, buprenorphine orpentazocine; or any pharmaceutically acceptable composition thereof.

In another aspect, the present invention provides for a pharmaceuticalcomposition for inhibition of opioid tolerance and opioidwithdrawal-induced hyperalgesia comprising: the compound DPI-125 havingthe structure of formula (I):

having the IUPAC name of(−)3-((S)-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)(3-thienyl)methyl)phenol,or pharmaceutically acceptable esters or salts thereof and apharmaceutically acceptable carrier.

Examples of pharmaceutically acceptable esters of the compound offormula (I) include carboxylic acid esters of the hydroxyl group in thecompound of formula (I) in which the non-carbonyl moiety of thecarboxylic acid portion of the ester grouping is selected from straightor branched chain alkyl (e.g., n-propyl, t-butyl, n-butyl), alkoxyalkyl(e.g., methoxymethyl), arylalkyl (e.g., benzyl), aryloxyalky (e.g.,phenoxymethyl), and aryl (e.g., phenyl); alkyl-, aryl-, orarylalkylsulfonyl (e.g., methanesulfonyl); amino acid esters (e.g.,L-valyl or L-isoleucyl); dicarboxylic acid esters (e.g., hemisuccinate);carbonate esters (e.g., ethoxycarbonyl); carbamate esters (e.g.,dimethylaminocarbonyl, (2-aminoethyl)aminocarbonyl); and inorganicesters (e.g., mono-, di- or triphosphate).

Pharmaceutically acceptable salts of an amino group include salts of:organic carboxylic acids such as acetic, citric, lactic, tartaric,malic, lactobionic, fumaric, and succinic acids; organic sulfonic acidssuch as methanesulfonic, ethanesulfonic, isethionic, benzenesulfonic andp-toluenesulfonic acids; and inorganic acids such as hydrochloric,hydrobromic, sulfuric, phosphoric and sulfamic acids. Pharmaceuticallyacceptable salts of a compound having a hydroxyl group consist of theanion of said compound in combination with a suitable cation such asNa+, NH4+, or NX4+(wherein X is for example a C1-4 alkyl group).

For therapeutic use, salts of the compound of formula (I) ispharmaceutically acceptable, i.e., salts derived from a pharmaceuticallyacceptable acid. However, salts of acids which are not pharmaceuticallyacceptable may also find use, for example, in the preparation orpurification of a pharmaceutically acceptable compound. All salts,whether or not derived from a pharmaceutically acceptable acid or base,are within the scope of the present invention.

Yet another aspect of the present invention relates to method oftreating a patient in need thereof with an opioid receptor agonisttherapeutic agent having activity on the mu, delta and kappa receptor,while attenuating respiratory depression incident to the administrationthereof, comprising administering to the patient an effective amount ofan opioid receptor agonist to attenuate the respiratory depression, theopioid receptor agonist compound DPI-125 having the formula:

(−)3-((S)-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)(3-thienyl)methyl)phenol,or esters or salts thereof.

Yet another aspect of the present invention relates to a pharmaceuticalcomposition comprising:

(a) an effective amount of a bioactive agent for treatment of acondition selected from the group consisting of drug addiction, drugoverdose or drug tolerance; and(b) an effective amount of a compound comprising the formula:

(−)3-((S)-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)(3-thienyl)methyl)phenolor a pharmaceutically acceptable salt or esters thereof.

The enantiomerically pure compound of the present invention can beco-administered with a bioactive agent that mediates respiratorydepression such as a mu receptor agonist, i.e., various analgesics, andaesthetics, and barbiturates. The vast majority of currently used highpotency analgesics, including morphine, alfantanil,morphine-6-glucoronide, oxymorphone, hydromorphone, oxycodone,hydrocodone, fentanyl, meperidine, sufentanyl and codeine, are mureceptor binding compounds. As is well established, these compounds,while highly efficacious for mediating analgesia, have accompanying sideeffects, including respiratory depression. The use of(−)3-((S)-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)(3-thienyl)methyl)phenolor ester or salt thereof according to the present invention may prevent,reduce, attenuate or even eliminate or reverse conditions in whichanalgesia induces respiratory depression, such as the respiratorydepression side effects normally attendant to the use of mu receptorbinding compounds.

Concerning drug addiction treatment with effective compounds within thebroad scope of the present invention, it is noted that methadone is amu-receptor opiate with actions similar to morphine, i.e., methadone isabusable and addictive. Methadone is used as a “maintenance therapy”agent for opiate addicts, so that such individuals can remain functionalwhile satisfying their addictions in a safer and non-criminal manner. Inthis respect, DPI-125 has utility in place of, or as an adjunct to,currently used treatments for drug addiction, such as those involvingnaltrexone, methadone, clonidine, etc.

In a still further aspect, the present invention provides for a methodof reducing dependence or tolerance on a dependence-inducing opiatedrug, the method comprising administering to a subject in need thereof atherapeutically effective amount of the compound DPI-125 having thestructure of formula (I):

having the IUPAC name of(−)3-((S)-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)(3-thienyl)methyl)phenol,or pharmaceutically acceptable esters or salts thereof.

Various other aspects, features and embodiments of the invention will bemore fully apparent from the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows Morphine Tolerance and the Effects of Morphine and DPI-125Challenge Doses

FIG. 2 shows DPI-125 Tolerance and the Effects of Morphine and DPI-125Challenge Doses.

FIG. 3 shows Dose response curves to morphine (s.c.) in male ratstolerant to morphine, DPI-125 or analgesic naïve.

FIG. 4 shows Dose response curves of DPI-125 in male rats tolerant toDPI-125, morphine sulfate or naïve to analgesic.

DETAILED DESCRIPTION OF THE INVENTION Definitions

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. As used herein the followingterms have the following meanings.

It must be noted that as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include plural referents unless thecontext clearly dictates otherwise. Thus, for example, reference to “acompound” includes a plurality of compounds.

The term “about” when used before a numerical designation, e.g.,temperature, time, amount, concentration, and such other, including arange, indicates approximations which may vary by (+) or (−) 10%, 5% or1%.

“Administration” refers to introducing an agent into a patient.Typically, an effective amount is administered, which amount can bedetermined by the treating physician or the like.

Any route of administration, such as oral, topical, subcutaneous,peritoneal, intra-arterial, inhalation, vaginal, rectal, nasal,introduction into the cerebrospinal fluid, or instillation into bodycompartments can be used. The agent may be administered by direct bloodstream delivery, e.g. sublingual, intranasal, or intrapulmonaryadministration.

The related terms and phrases “administering” and “administration of”,when used in connection with a compound or pharmaceutical composition(and grammatical equivalents) refer both to direct administration, whichmay be administration to a patient by a medical professional or byself-administration by the patient, and/or to indirect administration,which may be the act of prescribing a drug. For example, a physician whoinstructs a patient to self-administer a drug and/or provides a patientwith a prescription for a drug is administering the drug to the patient.

“Periodic administration” or “periodically administering” refers tomultiple treatments that occur on a daily, weekly, or monthly basis.Periodic administration may also refer to administration of DPI-125 orsalt or solvate thereof one, two, three, or more times per day.Administration may be via transdermal patch, gum, lozenge, sublingualtablet, intranasal, intrapulmonary, oral administration, or otheradministration.

“Comprising” or “comprises” is intended to mean that the compositionsand methods include the recited elements, but not excluding others.“Consisting essentially of” when used to define compositions andmethods, shall mean excluding other elements of any essentialsignificance to the combination for the stated purpose. Thus, acomposition consisting essentially of the elements as defined hereinwould not exclude other materials or steps that do not materially affectthe basic and novel characteristic(s) of the claimed invention.“Consisting of” shall mean excluding more than trace elements of otheringredients and substantial method steps. Embodiments defined by each ofthese transition terms are within the scope of this invention.

This invention is not limited to any particular chemical form of DPI-125and the drug may be given to patients either as a free base, solvate, oras a pharmaceutically acceptable acid addition salt.

“Pharmaceutically acceptable composition” refers to a composition thatis suitable for administration to a human. Such compositions includevarious excipients, diluents, carriers, and such other inactive agentswell known to the skilled artisan.

“Pharmaceutically acceptable salt” refers to pharmaceutically acceptablesalts, including pharmaceutically acceptable partial salts, of acompound, which salts are derived from a variety of organic andinorganic counter ions well known in the art and include, by way ofexample only, hydrochloric acid, hydrobromic acid, phosphoric acid,sulfuric acid, methane sulfonic acid, phosphorous acid, nitric acid,perchloric acid, acetic acid, tartaric acid, lactic acid, succinic acid,citric acid, malic acid, maleic acid, aconitic acid, salicylic acid,thalic acid, embonic acid, enanthic acid, oxalic acid and the like, andwhen the molecule contains an acidic functionality, include, by way ofexample only, sodium, potassium, calcium, magnesium, ammonium,tetraalkylammonium, and the like.

“Therapeutically effective amount” or “therapeutic amount” refers to anamount of a drug or an agent that, when administered to a patientsuffering from a condition, will have the intended therapeutic effect,e.g., alleviation, amelioration, palliation or elimination of one ormore manifestations of the condition in the patient. The therapeuticallyeffective amount will vary depending upon the patient and the conditionbeing treated, the weight and age of the subject, the severity of thecondition, the salt, solvate, or derivative of the active drug portionchosen, the particular composition or excipient chosen, the dosingregimen to be followed, timing of administration, the manner ofadministration and the like, all of which can be determined readily byone of ordinary skill in the art. The full therapeutic effect does notnecessarily occur by administration of one dose, and may occur onlyafter administration of a series of doses. Thus, a therapeuticallyeffective amount may be administered in one or more administrations. Forexample, and without limitation, a therapeutically effective amount ofDPI-125, in the context of treating opioid or opioid-like drugdependency, refers to an amount of that attenuates the dependency and/orsymptoms of acute withdrawal for at least 1 hours beyond control(placebo), at least 5 hours beyond control, and preferably at least 10hours beyond control.

A “therapeutic level” of a drug is an amount of DPI-125 orpharmaceutical salt or solvate thereof that is sufficient to treatopioid or opioid-like drug addiction or to treat, prevent, or attenuateacute withdrawal symptoms, but not high enough to pose any significantrisk to the patient. Therapeutic levels of drugs can be determined bytests that measure the actual concentration of the compound in the bloodof the patient. This concentration is referred to as the “serumconcentration.”

As defined herein, a “maintenance amount” of a drug is an amount,typically less than the therapeutically effective amount that providesattenuation and/or prevention of post-acute withdrawal syndrome in apatient. The maintenance amount of the compound is expected to be lessthan the therapeutically effective amount because the level ofinhibition does not need to be as high in a patient who is no longerphysically addicted to opioid or opioid-like drug. For example, amaintenance amount is preferably 80%, 70%, 60%, 50%, 40%, 30%, 20%, or10% less than a therapeutically effective amount, or any subvalue orsubrange there between.

“Treatment,” “treating,” and “treat” are defined as acting upon adisease, disorder, or condition with an agent to reduce or ameliorateharmful or any other undesired effects of the disease, disorder, orcondition and/or its symptoms. “Treatment,” as used herein, covers thetreatment of a human patient, and includes: (a) reducing the risk ofoccurrence of the condition in a patient determined to be predisposed tothe condition but not yet diagnosed as having the condition, (b)impeding the development of the condition, and/or (c) relieving thecondition, i.e., causing regression of the condition and/or relievingone or more symptoms of the condition. “Treating” or “treatment of” acondition or patient refers to taking steps to obtain beneficial ordesired results, including clinical results such as the reduction ofsymptoms. For purposes of this invention, beneficial or desired clinicalresults include, but are not limited to: treating opioid or opioid-likedrug addiction; opioid tolerance, treating, preventing, and/orattenuating acute withdrawal symptoms; treating, preventing, and/orattenuating long-term (post-acute) withdrawal symptoms; and preventingrelapse of opioid or opioid-like drug use.

As used herein, the term “opiate” refers to naturally-occurringalkaloids found in the opium poppy. These include codeine, morphine,oripavine, pseudomorphine, and thebaine. Also included are opium, opiumpoppy, poppy straw, and extracts and concentrates thereof.

As used herein, the term “opioid” refers to naturally-occurring opiatesand synthetic or semi-synthetic opioids that have psychoactive effects.Non-limiting examples include acetyl-alpha-methylphentanyl,acetylmethadol, alfentanil, allylprodine, alphacetylmethadol,alphamethadol, alpha-methylfentanyl, alpha-methylthiofentanyl,alphaprodine, anileridine, benzylmorphine, benzethidine,betacetylmethadol, beta-hydroxyfentanyl, beta-hydroxy-3-methylfentanyl,betameprodine, betacetylmethadol, beta-hydroxyfentanyl,beta-hydroxy-3-methylfentanyl, betameprodine, betamethadol, betaprodine,bezitramide, buprenorphine, butorphanol, carfentanil, clonitazene,codeine, desomorphine, dextromoramide, dextropropoxyphene, dezocine,diampromide, diamorphone, diethylthiambutene, dihydrocodeine,dihydroetorphine, dihydromorphine, dimenoxadol, dimepheptanol,dimethyl-thiambutene, dioxaphetyl butyrate, diphenoxylate, difenoxin,dipipanone, eptazocine, ethoheptazine, ethylmethylthiambutene,ethylmorphine, etonitazene, etorphine, etoxeridine, fentanyl,furethidine, heroin, hydrocodone, hydromorphone, hydroxypethidine,isomethadone, ketobemidone, levoalphacetylmethadol, levomethorphan,levorphanol, levophenacylmorphan, levomoramide, lofentanil, loperamide,laudanum, meperidine, meptazinol, metazocine, methadone,3-methylfentanyl, 3-methylthiofentanyl, metopon, morphine, morpheridine,MPPP (1-methyl-4-phenyl-4-propionoxypiperidine), myrophine, narceine,nicomorphine, noracymethadol, norlevorphanol, normethadone, nalorphine,nalbuphene, normorphine, norpipanone, opium, oxycodone, oxymorphone,papaveretum, para-fluorofentanyl, paregoric, PEPAP(1-(-2-phenethyl)-4-phenyl-4-acetoxypiperidine), pentazocine,phenadoxone, phenampromide, phenomorphan, phenazocine, phenoperidine,piminodine, piritramide, propheptazine, promedol, properidine, propiram,propoxyphene, racemoramide, racemethorphan, racemorphan, remifentanil,sufentanil, tapentadol, thiofentanyl, tilidine, tramadol, trimeperidine,mixtures of any of the foregoing, salts of any of the foregoing,derivatives of any of the foregoing, and the like. The term opioids alsoencompasses opioid intermediates, including4-cyano-2-dimethylamino-4,4-diphenyl butane,2-methyl-3-morpholino-1,1-diphenylpropane-carboxylic acid,4-cyano-1-methyl-4-phenylpiperidine,ethyl-4-phenylpiperidine-4-carboxylate, and1-methyl-4-phenylpiperidine-4-carboxylic acid. Many opioids are ScheduleI or Schedule II drugs in the US.

As used herein, the term “opioid-like drug” refers to any drug thatbinds to one or more opioid receptor and causes opioid-like addiction.Acute and long-term withdrawal symptoms from cessation of use of suchdrugs may be similar to those from cessation of opioids. Opioid-likedrugs include amphetamine, methamphetamine, ketamine, and cocaine.

As used herein, the terms “addiction” and “dependence” are usedinterchangeably to refer to the patient's inability to stop using theopioid or opioid-like drug, even when it would be in his/her bestinterest to stop. The DIAGNOSTIC AND STATISTICAL. MANUAL OF. MENTALDISORDERS. FOURTH EDITION. TEXT REVISION (DSMIV-TR) criteria fordependency include: Dependence or significant impairment or distress, asmanifested by 3 or more of the following during a 12 month period: 1.Tolerance or markedly increased amounts of the substance to achieveintoxication or desired effect or markedly diminished effect withcontinued use of the same amount of substance; 2. Withdrawal symptoms orthe use of certain substances to avoid withdrawal symptoms; 3. Use of asubstance in larger amounts or over a longer period than was intended;4. Persistent desire or unsuccessful efforts to cut down or controlsubstance use; 5. Involvement in chronic behavior to obtain thesubstance, use the substance, or recover from its effects; 6. Reductionor abandonment of social, occupational or recreational activitiesbecause of substance use; 7. Use of substances even though there is apersistent or recurrent physical or psychological problem that is likelyto have been caused or exacerbated by the substance.

The term “solvate” as used herein refers to complexes with solvents inwhich DPI-125 is reacted or from which DPI-125 is precipitated orcrystallized. For example, a complex with water is known as a “hydrate”.Solvates of DPI-125 are within the scope of the invention. It will beappreciated by those skilled in organic chemistry that many organiccompounds can exist in more than one crystalline form. For example,crystalline form may vary based on the solvate used. Thus, allcrystalline forms of DPI-125 or the pharmaceutically acceptable solvatesthereof are within the scope of the present invention.

DPI-125 of the present invention does not have seizure liability nordoes it exhibit dysphoria as a side effect in the first in human trial.Clearly an agonist with the ability to bind not only to the mu subtype,but also to the delta and the kappa subtypes offers a better approach.Mixed mu and delta opioid receptor agonists offer a clinical advantageof providing added analgesia with an improved therapeutic index andreduced risk of respiratory depression. Adding, kappa agonist activityhas been shown to reduce the euphoric effects associated with mureceptor activation, potentially resulting in reduced abuse potentialcompared to standard mu opiate agonists. There is no molecule with theagonist receptor profile of DPI-125 on the market or in development.

The present invention relates to a substantially enantiomerically purecompound of the formula:

(−)3-((S)-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)(3-thienyl)methyl)phenol,or esters or salts thereof.

The compound of formula (I), also referred to as DPI-125, acts as adelta-opioid agonist in the mouse vas deferens delta receptor subtype,as well as an agonist at the delta receptor in the mouse brain, anempirically distinguishable delta receptor subtype from the deltareceptor in the mouse vas deferens. Also, the compound has activity atthe mu-opioid receptor and exhibits affinity for the kappa receptor.

Subjects to be treated by the methods of the present invention includeboth human and non-human animal (e.g., bird, dog, cat, cow, horse)subjects, and are preferably mammalian subjects, and most preferablyhuman subjects.

Depending on the specific condition to be treated, animal subjects maybe administered the compound of formula (I) at any suitabletherapeutically effective and safe dosage, as may readily be determinedwithin the skill of the art, and without undue experimentation.

In general, while the effective dosage of the compound of the inventionfor therapeutic use may be widely varied in the broad practice of theinvention, depending on the specific application, condition, or diseasestate involved, as readily determinable within the skill of the art,suitable therapeutic doses of the formula (I) compound or esters orsalts thereof, for each of the appertaining compositions describedherein, and for achievement of therapeutic benefit in treatment of eachof the conditions described herein, typically in the range of 0.01microgram (μg) to 50 milligrams (mg) per kilogram body weight of therecipient, and preferably in the range of 5 μg to 20 mg per kilogrambody weight and depending on the route of administration.

The desired dose is preferably presented as once, two, three, four,five, six, or more sub-doses administered at appropriate intervalsthroughout the day. Alternatively, if the condition of the recipient sorequires, the doses may be administered as a continuous infusion orcontinuous exposure through a depot formulation.

The mode of administration and dosage forms will of course affect thetherapeutic amount of the compound that is desirable and efficacious forthe given treatment application. For example, orally administereddosages typically are at least twice, e.g., 2-10 times, the dosagelevels used in parenteral administration methods, for the same activeingredient.

The compound of formula (I) may be administered per se as well as in theform of pharmaceutically acceptable ethers, esters, salts, and otherphysiologically functional derivatives thereof.

The formulations include those suitable for parenteral as well asnon-parenteral administration, and specific administration modalitiesinclude oral, rectal, topical, nasal, ophthalmic, subcutaneous,intramuscular, intravenous, transdermal, spinal, intrathecal,intra-articular, intra-arterial, sub-arachnoid, sublingual, oralmucosal, bronchial, lymphatic, and intra-uterine administration.Formulations suitable for parenteral and oral administration arepreferred.

When the active agent of formula (I) is utilized in a formulationcomprising a liquid solution, the formulation advantageously may beadministered parenterally. When the active agent is employed in a liquidsuspension formulation, the formulation may be advantageouslyadministered orally, rectally, or bronchially.

When the active agent is utilized directly in the form of a powderedsolid, the active agent may advantageously be administered orally orsublingually. Alternatively, it may be administered bronchially, vianebulization of the powder in a carrier gas, to form a gaseousdispersion of the powder which is inspired by the patient from abreathing circuit comprising a suitable nebulizer device.

In some applications, it may be advantageous to utilize the activecompound of formula (I) in a “vectorized” form, such as by encapsulationof the active agent in a liposome or other encapsulant medium, or byfixation of the active compound, e.g., by covalent bonding, chelation,or associative coordination, on a suitable biomolecule, such as thoseselected from proteins, lipoproteins, glycoproteins, andpolysaccharides.

The formulations comprising the active compound of formula (I) mayconveniently be presented in unit dosage forms and may be prepared byany of the methods well known in the art of pharmacy. Such methodsgenerally include the step of bringing the active compound intoassociation with a carrier which constitutes one or more accessoryingredients. Typically, the formulations are prepared by uniformly andintimately bringing the active compound into association with a liquidcarrier, a finely divided solid carrier, or both, and then, ifnecessary, shaping the product into dosage forms of the desiredformulation.

Formulations of the present invention suitable for oral administrationmay be presented as discrete units such as capsules, cachets, tablets,or lozenges, each containing a predetermined amount of the activeingredient as a powder or granules; or a suspension in an aqueous liquoror a non-aqueous liquid, such as a syrup, an elixir, an emulsion, or adraught.

A tablet may be made by compression or molding, optionally with one ormore accessory ingredients. Compressed tablets may be prepared bycompressing in a suitable machine, with the active compound being in afree-flowing form such as a powder or granules which optionally is mixedwith a binder, disintegrant, lubricant, inert diluent, surface activeagent, or discharging agent. Molded tablets comprised of a mixture ofthe powdered active compound with a suitable carrier may be made bymolding in a suitable machine.

A syrup may be made by adding the active compound to a concentratedaqueous solution of a sugar, for example sucrose, to which may also beadded any accessory ingredient(s). Such accessory ingredient(s) mayinclude flavorings, suitable preservative, agents to retardcrystallization of the sugar, and agents to increase the solubility ofany other ingredient, such as a polyhydroxy alcohol, for exampleglycerol or sorbitol.

Formulations suitable for parenteral administration comprise a sterileaqueous preparation of the active compound, which preferably is isotonicwith the blood of the recipient (e.g., physiological saline solution).Such formulations may include suspending agents and thickening agents,liposomes or other microparticulate systems which are designed to targetthe compound to blood components or one or more organs. The formulationsmay be presented in unit-dose or multi-dose form.

Nasal spray formulations comprise purified aqueous solutions of theactive compound of formula (I) with preservative agents and isotonicagents. Such formulations are preferably adjusted to a pH and isotonicstate compatible with the nasal mucous membranes. Formulations forrectal administration may be presented as a suppository with a suitablecarrier such as cocoa butter, hydrogenated fats, or hydrogenated fattycarboxylic acids. Ophthalmic formulations are prepared by a similarmethod to the nasal spray, except that the pH and isotonic factors arepreferably adjusted to match that of the eye.

The compounds of the invention may also be delivered through the skin ormuscosal tissue using conventional transdermal drug delivery systems,i.e., transdermal “patches” wherein a composition of the presentinvention is typically contained within a laminated structure thatserves as a drug delivery device to be affixed to the body surface. Insuch a structure, the pharmaceutical composition is typically containedin a layer, or “reservoir,” underlying an upper backing layer. Thelaminated device may contain a single reservoir, or it may containmultiple reservoirs. In one embodiment, the reservoir comprises apolymeric matrix of a pharmaceutically acceptable contact adhesivematerial that serves to affix the system to the skin during drugdelivery. Alternatively, the active agent-containing reservoir and skincontact adhesive are present as separate and distinct layers, with theadhesive underlying the reservoir which, in this case, may be either apolymeric matrix as described above, or it may be a liquid or gelreservoir, or may take some other form. The backing layer in theselaminates, which serves as the upper surface of the device, functions asthe primary structural element of the laminated structure and providesthe device with much of its flexibility. The material selected for thebacking layer should be substantially impermeable to the active agentand any other materials that are present.

In addition to the aforementioned ingredients, formulations of thisinvention may further include one or more accessory ingredient(s)selected from diluents, buffers, flavoring agents, binders,disintegrants, surface active agents, thickeners, lubricants,preservatives (including antioxidants), and the like.

The present invention also contemplates a process for the preparation of(−)3-((S)-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)(3-thienyl)methyl)phenolor an ester or salt thereof to synthesize an essentiallyenantiomerically pure opioid receptor agonist that is substantially freeof its stereoisomer.

Such compound is desirably prepared in substantially pure enantiomerform, with an enantiopurity of at least 98% EE, and most preferably atleast 99% EE. Enantiomeric excess values provide a quantitative measureof the excess of the percentage amount of a major isomer over thepercentage amount of a minor isomer which is present therewith, and maybe readily determined by suitable methods well-known and established inthe art, as for example chiral high pressure liquid chromatography(HPLC), chiral gas chromatography (GC), nuclear magnetic resonance (NMR)using chiral shift reagents, etc.

The use of(−)3-((S)-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)(3-thienyl)methyl)phenolor ester or salt thereof according to the present invention may prevent,reduce, attenuate or even eliminate or reverse conditions such as therespiratory depression side effects normally attendant to the use of mureceptor binding compounds.

Thus, the present invention contemplates co-administration of(−)3-((S)-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)(3-thienyl)methyl)phenolwith drug agents mediating respiratory depression, in which the compoundof the present invention is administered in an amount effective tocombat, e.g., significantly attenuate, and preferably substantiallyeliminate, the respiratory depression incident to the use of therespiratory depression-mediating agent.

Thus, the compounds of the invention have broad utility in surgical andclinical care applications, to combat the unwanted respiratorydepression side effect incident to the use of such commonly used drugsas morphine and fentanyl.

Example 1

Set out below is the synthesis scheme for production of(−)3-((S)-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)(3-thienyl)methyl)phenol.

A solution of 3-bromophenol (400 g, 2.31 mol),tert-butylchlorodimethylsilane (391 g, 2.54 mol), and imidazole (346 g,5.08 mol) in 5000 mL of dichloromethane was stirred overnight at roomtemperature. The reaction solution was poured into 2000 mL of water andthe layers were separated. The organic layer was washed with 1N aqueoussodium hydroxide solution (3×1500 mL) and water (2×1500 mL) beforepassing through a pad of silica gel (400 g, silica 60, 230-400 mesh).The silica gel was washed with dichloromethane (2×500 mL), the filtrateswere combined and the solvent removed under reduced pressure to give 669g (98.4%) of 3-(bromophenoxy)-tert-butyldimethylsilane as a clear paleyellow liquid. NMR (300 MHz, CDCl₃): δ 0.2 (s, 6H); 1.0 (s, 9H); 6.75(m, 1H); 7.0 (br s, 1H); 7.1 (m, 2H).

3-tert-Butyldimethylsilyloxyphenylmagnesium bromide was formed by theslow addition of a mixture 3-bromophenoxy-tert-butyldimethylsilane (118g, 400 mmol) and dibromoethane (15 g, 80 mmol) in 400 mL ofinhibitor-free anhydrous tetrahydrofuran to a solution of magnesiumturnings (15.5 g, 640 mmol) in 800 mL of inhibitor-free anhydroustetrahydrofuran at reflux. After stirring for one hour at reflux thelight brown clear mixture was cooled to room temperature.

Doubly distilled thiophene-3-carboxaldehyde (2.46 g, 22 mmol),benzotriazole (2.62 g, 22 mmol),(2R,5S)-1-allyl-2,5-trans-dimethylpiperazine (3.39 g, 22 mmol, ChirotechTechnology, Ltd., Cambridge, England) and p-toluenesulfonic acidmonohydrate (209 mg, 1.1 mmol) were dissolved in 125 mL toluene andheated to a gentle reflux. The water-toluene azeotrope was collected ina Dean-Stark trap over the course of 2.5 hours. The remaining solventwas removed under vacuum. The residue was dissolved in 25 mL anhydrousinhibitor-free tetrahydrofuran and to this was added a solution of3-tert-butyldimethylsilyloxyphenylmagnesium bromide in tetrahydrofuran(125 mL, 0.32 M) under a nitrogen atmosphere at 20-25° C.

The reaction was stirred at 40° C. for 2 hours and then quenched by theaddition of 25 mL of saturated NH₄Cl solution. Anhydrous magnesiumsulfate (˜5 g) and Celite (˜10 g) were added. The mixture was stirredand filtered, and the solvent was removed under reduced pressure. Theresidue was dissolved in ethyl acetate (200 mL) and washed with 1 N NaOHsolution (3×100 mL), water (1×100 mL) and brine (1×100 mL). The solutionwas then concentrated under reduced pressure.

The dark residue was dissolved in 50 mL anhydrous tetrahydrofuran andtetrabutyl-ammonium fluoride dihydrate (8.63 g, 33 mmol) was added.After stirring for 2 hours the reaction was concentrated and the residuewas dissolved in 100 mL of ethyl acetate. The mixture was extracted withdilute NaHCO₃ solution (3×75 mL) and with water (1×75 mL). The organiclayer was diluted with 100 mL of methyl t-butyl ether and extracted with1% citric acid solution (3×100 mL). The combined aqueous extracts werevacuum filtered through a 0.45 micron membrane filter and the filtrateadjusted to pH 8.5 using 50% NaOH solution before it was extracted withdichloromethane (2×100 mL). The solution was dried azeotropically whenconcentrated under reduced pressure. The resulting tan glassy solid (3.6g, 10.5 mmol, 47.8%) was crystallized from 43 mL of45:55/2-propanol:water and recrystallized from 20 mL of1:1/2-propanol:water to yield fluffy, white needle crystals (2.1 g, 6.13mmol, 28% based on chiral piperazine), [α]_(D) ²⁰=−8.33° (abs. ethanol,c=1.0). ¹H NMR (500 MHz, d₆-DMSO): δ 9.32 (s, 1H), 7.44 (dd, J=3.2, 4.9Hz, 1H), 7.15 (s, 1H), 7.13 (t, J=8.25 Hz, 1H), 6.98 (d, J=4.9 Hz, 1H),6.66-6.70 (m, 3H), 5.73-5.81 (m, 1H), 5.15 (d, J=17.1 Hz, 1H), 5.09 (d,J=10.5 Hz, 1H), 5.02 (s, 1H), 3.20 (br d, J=10.2 Hz, 1H), 2.78 (dd,J=7.3, 7.5 Hz, 1H), 2.68 (dd, J=2.6, 11.3 Hz, 1H), 2.59 (dd, J=1, 9.3Hz, 1H), 2.44 (br s, 2H), 2.02 (t, J=8.6 Hz, 1H), 1.81 (t, J=8.1 Hz,1H), 1.09 (d, J=6 Hz, 3H), 0.91 (d, J=6 Hz, 3H).

Calculated for C₂₀H₂₆N₂OS: C, 70.14; H, 7.65; N, 8.18; S, 9.36%.

Found: C, 70.19; H, 7.58; N, 8.12; S, 9.33%.

Example 2

Binding of Dpi-125 to Three Opioid Receptors

DPI-125 was evaluated for in vitro opioid receptor affinity in rat brainmembranes (and 6 opioid) and guinea pig cerebellum (κ opioid receptor).Membranes for radioligand binding were prepared from either rat wholebrain or guinea pig cerebellum, supplied by Pel-Freeze Biological Inc.(Rogers, Ark.). Tissues were homogenized in 50 mM TRIS(Tris[hydrooxymethyl]aminomethane) buffer (pH 7.4) containing 50 μg/mlsoybean trypsin inhibitor, 1 mM EDTA (Ethylenediaminetetraacetic acid),and 100 μM PMSF (Phenylmethylsulfonyl fluoride). The homogenized braintissues were centrifuged at 500×g for 30 minutes (4° C.) to remove largedebris. The supernatant was polytronically sonicated for 10 seconds(P.E. setting of 2, 4° C.). Sucrose solution was then added to a finalconcentration of 0.35 M using a 10 mM TRIS-Sucrose buffer (pH 7.4) andthe brain membranes were then centrifuged at 40,000×g for 30 minutes (4°C.). The membrane pellets were then washed twice in 10 mM TRIS buffer(pH 7.4) containing 50 μg/ml soybean trypsin inhibitor, 1 mM EDTA, and100 μM PMSF.

Radioligand binding assays were performed in 10 mM TRIS buffer (pH 7.4)containing 50 μg/ml soybean trypsin inhibitor, 1 mM EDTA, 5 mM MgCl₂,and 100 μM PMSF. Tritium-labeled DAMGO (μ), Deltorphin II (δ), or U69593(κ) purchased from New England Nuclear were used as ligands incompetitive experiments (2-3×10⁻¹⁰ M final concentrations) withnon-specific binding defined by 0.5×10⁻⁶ M Naloxone (purchased fromSIGMA Chemical Co.). All binding assays were run at room temperature for90 minutes and then terminated by rapid filtration on GF/C glass fiberfilters (Whatman, Hillsboro, Oreg.) with 50 mM TRIS buffer (4° C., pH7.4) employing a Brandel Semi-automatic Cell Harvester (Model M48,Brandel, Gaithersburg, Md.). The filters were washed twice with 50 mMTRIS buffer (4° C., pH 7.4) and the filters were placed in liquidscintillation cocktail and the bound radioactivity counted on a BeckmanLS 6500 scintillation counter. The potency of the compounds ininhibiting the binding of radiolabelled DAMGO (μ), Deltorphin II (δ), orU69593 (κ) was determined from full concentration-effect curves. Withthe computer program Prism (GraphPad Software Inc., San Diego, Calif.)the IC₅₀ values were determined using a one-site nonlinear regressionanalysis of the radioligand binding data. The IC₅₀ values were thenconverted to K_(i) values using the Cheng-Prusoff equation. ³⁵ (DPI-125)Enantiomer of the present invention(−)3-((S)-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)(3-thienyl)methyl)phenol(SSR) was tested and the results for such binding assays is set forthbelow in Table I:

TABLE I Rat Brain Guinea Pig Membrane Brain Membrane K_(i) (nM) K_(i)(nM) Compound μ δ κ Enantiomer 0.40 0.88 1.77 DPI-125 (SSR)

Results: It is evident that DPI-125 compound exhibits distinct anddifferent binding affinity for the different types of receptors tested.The strong and increased affinity of the compound DPI-125 for both muand delta and kappa receptors is shown by the very low concentrationrequired to inhibit the binding of the labeled compounds.

Example 3

In the rat tail-pinch model, DPI-125 was 47 times more potent thanmorphine in exhibiting antinociceptive activity. As anticipated, DPI-125has a much larger therapeutic index (antinociception versus respiratorydepression) than morphine. Comparing ED50 values in rats forantinociceptive effects and respiratory depression (increased PaCO2),the therapeutic index for DPI-125 was approximately 7× higher than formorphine (Table 2).

Analgesic Respiratory ED₅₀ Depression Tail Pinch ED₅₀ Therapeutic Drug(mg/kg) (mg/kg) Ratio Morphine 2.01 4.23 2.1 Alfentanil 0.0034 0.01273.7 DPI-3290 0.050 0.91 18.2 DPI-125 0.050 0.72 14.4

Table 2: Reduced Potential for Respiratory Depression with Mixed OpioidAgonists. DPI-125 demonstrates comparable analgesic/antinociceptivecapacity to morphine and alfentanil with the substantially reduced sideeffect of respiratory depression, presenting with a much greatertherapeutic index

The preclinical toxicity profile of DPI-125 was as expected for anopioid compound, with two positive exceptions. First, the emesis oftenassociated with other opioid analgesics did not occur, even at thehighest doses given. Second, DPI-125 did not produce any flushing,reddened mucous membranes or urticaria as seen with IV doses of otheropioid analgesics.

Given this positive preclinical data, Good Laboratory Practice (GLP)Investigational New Drug (IND) enabling toxicology studies wereperformed. DPI-125 was tested in human subjects in a PK and safetystudy. DPI-125.IV.001, was a randomized, single-center, double-blind,placebo-controlled, dose escalating Phase 1 study. The primary objectivewas to evaluate the safety of single doses of DPI-125 administered byintravenous bolus infusion in normal healthy adult subjects. Male andfemale subjects between 18 and 55 years of age, inclusive, who were ingood health and who were not taking any medications were eligible forenrollment. For each dose group, cohorts of 6 subjects were randomizedto receive either placebo (n=1) or DPI-125 for Injection (n=5) as asingle bolus dose of 5, 10, 20, or 50 μg/kg administered over 2 minutes.A final cohort received 25 μg/kg administered over 1 minute. For thisfirst in human study, it was decided that 50 μg/kg should be the highestdose to be tested so the maximum tolerated dose was not determined.

DPI-125 for injection was well tolerated; there were no deaths or anyother serious AEs reported. Drug-related AEs were generallydose-dependent and all resolved spontaneously; none led todiscontinuation. The most common drug-related AEs were somnolence,dizziness, and paraesthesia, interestingly, not nausea or vomiting. Nosubject had a clinically significant change in vital sign measurements,on physical examination, 12-lead electrocardiogram (“ECG”), orcontinuous lead-II ECG. No time- or dose-related trends in corrected QTintervals were noted. Overall, electroencephalogram (“EEG”) tracingswere unremarkable, with no changes associated with the administration ofstudy drug and, in particular, no seizure activity was noted. No subjecthad a clinically significant change in laboratory results. Inconclusion, there were no findings of clinical concern at any dose ofDPI-125 tested in this study.

The preliminary studies indicate that DPI-125 has analgesic benefitspotentially superior to morphine and comparable to fentanyl but inaddition it will have a far better tolerability profile. Notably, itoffers a larger safety margin for respiratory depression and may reduceabuse potential. There is currently no drug like DPI-125 (mu, kappa anddelta mixed agonists) either on the market or in development. Theresults indicate that DPI-125 provides analgesic benefits of superior orcomparable potency to current opioids (>40× that of morphine) anddemonstrates lack of abuse liability by not demonstrating reinforcingeffects at doses that achieve strong analgesia in contrast to thatobserved with currently marketed opioids.

Example 4

Evaluation of the analgesic effect of DPI-125 in Non Human Primates(NHPs) at 3 different doses. Capsaicin evokes pain sensation byactivating the transient receptor potential vanilloid type 1 which playsa pivotal role in diverse pain states.²³ Capsaicin has been widelyutilized as a clinically relevant pain model in humans to study painprocessing pathways and to identify potential analgesics.^(24,25) Amodel of capsaicin-induced thermal allodynia has been established andused to evaluate the functional efficacy of clinically used opioids andexperimental compounds for alleviating capsaicin-inducedhypersensitivity in NHP.^(26,27) The study provides for documentation ofthe functional efficacy of DPI-125 as an analgesic in primates comparedto fentanyl.

Briefly, 0.3 mL of capsaicin at 1.2 mg/mL is administered topically viaa bandage attached on the terminal 3-5 cm of the tail for 15 min.Capsaicin-induced hypersensitivity peaks at 15 min after removal of thecapsaicin bandage and this is the time point used to measure non-humanprimates' (NHP) behavioral responses (i.e., reversal of reducedtail-withdrawal latency in 46° C. water).²⁶

Effects of systemic DPI-125 (0, 0.1, 0.3, and 1 mg/kg, IV) isinvestigated in the same group of 4 subjects. The dose range of DPI-125is selected and projected from the active dose range in rodents.Normally, 3 doses are selected to demonstrate a dose dependency for anystudy endpoint. The dose of DPI-125 will either be increased ordecreased based on results of this tentative dose range in order tocomplete a dose-response study.

For comparison, effects of fentanyl (0.01 mg/kg, IV)²⁸ is also be testedand used as a positive control in the same subjects. Using a singledosing procedure (i.e., drug pretreatment 20 min before capsaicin), theeffectiveness and potency of DPI-125 is determined for alleviatingcapsaicin-induced hypersensitivity. Based on prior experience acrossdifferent ligands and experimental settings²⁹⁻³¹, a 1-weekinter-injection interval (i.e., NHP subjects are tested once per week)is sufficient to avoid potential confounding factors under theseexperimental conditions. The order of administration of vehicle anddifferent doses of DPI-125 is randomized and scheduled according to aLatin Square design.

Example 5

Evaluation of Reinforcing Behaviour of DPI-125 on IV DrugSelf-administration in NHPs: A progressive-ratio (PR) schedule ofreinforcement which has been commonly used for evaluating abuseliability^(26,32,33) is used to determine the relative reinforcingstrength of DPI-125 as compared to another mu opioid analgesic,fentanyl, which exerts high reinforcing strength. The PR schedulemeasures how many responses subjects will emit in order to receive adrug injection before they cease responding. The advantage of this PRschedule for assessing abuse liability is that it can provide adifferentiation among drugs that may function as positive reinforcers.³³Dose-response curves are determined by substituting vehicle, iv fentanyl(0.0003 mg/kg/injection), and a range of doses of DPI-125 (0.001-0.01mg/kg/injection) in a random order. These dosing conditions areavailable for at least five consecutive sessions and until NHP'sresponses become stable.²⁶ This study determines whether DPI-125produces reinforcing strength in comparison to fentanyl as an indicationof its abuse potential.

Data Analysis/Statistical Analysis: In the Vertebrate Animals Section,we have justified n=4NHPs is sufficient to provide the statistical powerand it can be used to determine and compare the behavioral effects ofDPI-125 by citing several references. For highly addictive drugs likecocaine, the averaged injection numbers by NHPs under the PR scheduleare around 12-15. In contrast, the averaged injection number forsaline/vehicle is around 3-4.²⁶ If the averaged injection number earnedfor DPI-125 (over several doses) is significantly lower than 12 and notsignificantly different from saline/vehicle, i.e., 3-4, then it isconcluded that DPI-125 does not have reinforcing strength, i.e., noconcern for its abuse liability.

Example 6

As stated above, tolerance is typically a decrease in drug effect withrepeated or chronic dosing. In the treatment of chronic pain, the painkiller loses its effect and the subject remains in pain despite theadministration of the same dose of opioid.

Three studies were conducted to assess the degree of antinociceptivetolerance produced by chronic administration of DPI-125 and the degreeof cross-tolerance to morphine.

The objective of study 1 was to demonstrate the presence or absence ofcross-tolerance between morphine and DPI-125. The objective of studies 2and 3 was to evaluate the degree of cross-tolerance in terms of changesin the analgesic ED50 for DPI-125 and morphine. This study was performedin three parts to investigate the development of tolerance to theantinociceptive effects of equi-analgesic doses of DPI-125 and morphinesulfate (morphine) and to identify any cross-tolerance between these twoopioid receptor agonists.

After twice daily dosing of 5.0 mg/kg morphine (s.c.) for 5 days or 1.0mg/kg DPI-125 (s.c.) for 6 days in male Sprague-Dawley rats, toleranceto the antinociceptive effects of both drugs were detected in the rattail pinch assay. Tolerance did not develop after a single dose ofmorphine or DPI-125. There was a clear difference in the rate ofdevelopment of tolerance to morphine and DPI-125 administered in thismanner. Maximal tolerance to the antinociceptive effects of morphine wasevident at day 5 for dosing, whereas complete tolerance to DPI-125 wasnot evident until day 8. Animals tolerant to 1.0 mg/kg DPI-125 BIDshowed complete tolerance to the antinociceptive effects of 5.0 mg/kgmorphine. However, animals tolerant to 5.0 mg/kg morphine BID were onlypartially tolerant to 1.0 mg/kg DPI-125. The antinociceptive ED50 formorphine and DPI-125 was determined in animals exposed to vehicle orexposed and tolerant to either morphine or DPI-125. The results arepresented in the table below.

Confidence Fold Drug Treatment ED₅₀ Interval Change Morphine to naiveanimals 2.037 1.509-2.750 Morphine to morphine tolerant animals 11.268.115-15.64 5.5 Morphine to DPI-125 tolerant animals 15.82 13.25-18.907.8 DPI-125 to naïve animals 0.407 0.265-0.625 DPI-125 to DPI-125tolerant animals 1.218 1.211-1.226 3.0 DPI-125 to morphine tolerantanimals 0.717 0.671-0.766 1.8

In summary, mild DPI-125 tolerance developed over several days of twicedaily dosing at 2.0 mg/kg/day. Tolerance to DPI-125 crossed overcompletely and tolerance to morphine was also present. However,following the development of complete tolerance to morphine (10.0mg/kg/day), DPI-125 still remained effective as an antinociceptive agentat 2.0 mg/kg/day. Thus tolerance to DPI-125 is not as great as that tomorphine.

Materials and Methods

Dose solutions were prepared daily just before the first daily dose wasadministered. Dose solutions of DPI-125 were prepared in 5% Dextrose inwater (USP) with an acetic acid/sodium acetate buffer according to theprocedure in the study protocol. Dose solutions of morphine sulfate(Sigma-Aldrich) were prepared in 5% Dextrose in water (USP). Dosesolutions were stored between doses at room temperature, protected fromlight.

This study was performed in three parts to investigate the developmentof tolerance to the antinociceptive effects of equi-analgesic doses ofDPI-125 and morphine sulfate (morphine) and to identify anycross-tolerance between these two opioid receptor agonists. Theequi-analgesic doses used to induce tolerance to the antinociceptiveeffects of morphine and DPI-125 were selected based on theantinociceptive ED50 for each compound. ED50 values were taken from bothinternal and published data and the doses used here were ˜2.5 fold theantinociceptive ED50 dose.

Study 1:

Male Sprague-Dawley rats were used in this study in two groups of 12animals. The first group received subcutaneous (s.c) doses of 5.0 mg/kgof morphine sulfate twice a day (doses were 6 hours apart) totaling adaily dose of 10 mg/kg. The second group in this study receivedsubcutaneous doses of 1.0 mg/kg DPI-125 twice daily (doses wereseparated by 6 hours). Dosing was repeated for 5 days in the case ofmorphine sulfate administration and for 6 days in the case of DPI-125.The first day of dosing was designated day 1. On day 6 (morphine sulfatetreated group) or day 7 (DPI-125 treated group), half the subjects ofboth groups (i.e. 6 animals) were challenged with a singleadministration of the drug not received during the first 5 or 6 testdays. The other half received the same drug as in the previous 5 or 6days. On each day, animals were tested for antinociception 20 and 30minutes following drug administration using the standard tail pinchtest. Where complete cross-tolerance was not observed, challenge dosingcontinued on a twice daily schedule (separated by 6 hours) untilcomplete tolerance to antinociceptive effects were observed, at whichtime both groups were then euthanized.

Study 2:

Dosing and antinociception testing was the same as described in Study 1using similar sized groups (n=6). All doses were administeredsubcutaneously twice daily at half the total daily dose. Doses wereseparated by 6 hours. Antinociceptive drug effects were assessed 20 and30 minutes after every dose administered using a tail pinch test. As aresult of the findings from the first study showing no difference inthese time points, only the 20 minute test time was used for in depthanalysis. The first day of dosing was designated as day 1. Dose groupsand challenge doses are listed in Table 1. Groups 1-3 received asubcutaneous dose of dextrose on days 1-6. On day 7 each group receivedeither a 2.0, 3.0 or 10.0 mg/kg/day dose of morphine sulfate(respectively). Groups 4-7 received 5.0 mg/kg/day morphine sulfate ondays 1-6 but received different challenge doses of morphine sulfate onday 7. Challenge doses were 15.0, 20.0 and 25.0 mg/kg/day for groups 4,5 and 6 respectively. Groups 8-11 received 5.0 mg/kg/day doses ofmorphine sulfate on day 1-6. On day 7, challenge doses of DPI-125 wereadministered at doses of 0.5, 1.0, 2.0 and 3.0 mg/kg/day for groups 8,9, 10, and 11 respectively. A total of 18 animals received controlsolution for the first six days; a total of 48 animals received morphinesulfate for the first six days.

Study 3:

Dosing and antinociception testing was the same as described in Study 1using similar sized groups (n=6). All doses were administeredsubcutaneously twice daily at half the total daily dose. Doses wereseparated by 6 hours. Antinociceptive drug effects were assessed 20 and30 minutes after every dose administered using a tail pinch test. As aresult of the findings from the first study showing no difference inthese time points, only the 20 minute test time was used for in depthanalysis. The first day of dosing was designated as day 1. Dose groupsand challenge doses are listed in Table 2. Groups 12-14 receiveddextrose on days 1-6. On day 7 these groups received 0.25, 0.5 or 1.0mg/kg/day of DPI-125, respectively. Groups 15-18 received 1.0 mg/kg/dayDPI-125 on days 1-6 and received a challenge dose of 2.25, 2.5, 3.0, 3.5mg/kg/day of DPI-125 respectively on day 7. Groups 19-22 received 1.0mg/kg/day doses of DPI-125 on days 1-6. On day 7, these groups receivedchallenge doses of 20.0, 30.0, 40.0, and 50.0 mg/kg/day of morphinesulfate respectively. All groups were euthanized and discarded on Day 7.A total of 18 animals received control solution for the first 6 days; atotal of 48 animals received DPI-125 for the first six days.

Antinociception:

A trained observer blinded to the drug treatment allocation assessedantinociception using an arterial clamp on the tail, at a pointapproximately one inch from the tip, at 20 and 30 minutespost-injection. The escape latency was determined by measuring the timefrom the placement of the clamp to the detection of an escape response(either an attempt to bite the clamp or vocalization). A 20 secondcutoff period was used to prevent tissue damage during antinociceptivetesting. Drug-induced antinociception was converted to Maximal PercentEffect (MPE) values by expressing the response latency in seconds as apercentage of the maximal response time (20 seconds). No formalstatistical analysis of the difference between the antinociceptioninduced by the first and second doses of drug on the first test day wasperformed to investigate the incidence of tolerance after a single drugdose since, with both morphine sulfate and DPI-125, MPE was 100% for allanimals at both dose points and time points on Day 1. Subsequently, forgraphical representation, all dose time points were expressed in daysnumbered from the first dose on the first day of dosing (Day 1) and thesecond daily dose (6 hours after the first dose) as the quarter day (Day1.25).

Study 1:

Tolerance to the antinociceptive effects of morphine sulfate and DPI-125was analyzed using analysis of variance over the first 6 days of drugadministration and at each tail pinch test time (20 or 30 minutespost-drug). Post-hoc analysis was performed using a Fisher's PredictedLeast Squared Difference (FPLSD) test (Statview, SPSS, NC). Challengedoses were compared to the first and last doses of the toleranceschedule (i.e. day 1 and day 5 dose 2 for morphine tolerant animals andday 1 and day 6 dose 2 for the DPI-125 tolerant animals) in a similarmanner (ANOVA+FPLSD). The difference between the 20 minute and 30 minutepost-dose tail pinch time points was compared using a repeated measuresanalysis of variance for the morphine and DPI-125 tolerance schedulesonly (not the challenge dosing). Significant main effects were analyzedusing pair wise Student's t-test comparisons. All tests requiredsignificance at P<0.05 in a two-tailed test.

Studies 2 and 3:

Data from studies 2 and 3 were expressed in MPE as described above.Non-linear regression was used to determine ED50 values for morphinesulfate and DPI-125 in naïve animals and animals tolerant to eithermorphine sulfate or DPI-125 (Prism, GraphPad Software, CA). ED50 valuesare presented with 95% confidence intervals as follows: ED50(lower-upper limit of 95% interval).

Results

Study 1 Tolerance to Morphine Sulfate:

FIG. 1 shows the MPE antinociceptive response to 10.0 mg/kg/day (5.0mg/kg/dose) morphine sulfate over repeated doses/days at both the 20 and30 minute post-drug time points. Repeated measures analysis of varianceshowed no significant difference between the tolerance profile ofrepeated morphine sulfate dosing when antinociception was determined at20 or 30 minutes post-drug (F(1,132)=0.074; P=0.787).

Tolerance to the Antinociceptive Effects of Morphine Sulfate:

There was no significant difference between the effect of the first andsecond morphine sulfate dose on day 1 (100% MPE for all animals at bothdoses). Significant tolerance to morphine sulfate-inducedantinociception developed by the 3rd dose (the first dose on day 2) atboth the 20 minute (78.9±7.9%; P<0.05) and 30 minute (78.9±8.6%;P<0.005) post-drug assessment times. Complete desensitization toantinociceptive effects (0% MPE) did not develop on any day at eitherthe 20 or 30 minute assessment times. However, by the second dose of day4, sufficient tolerance had developed that morphine sulfate produced amean MPE of 7.0±2.8% at 20 minutes post-drug (P<0.0001 v. dose 1) and5.7±1.8% at 30 minutes post-drug (P<0.0001 v. dose 1). The lowest MPEvalue was produced after the first dose day 5 and produced a mean MPE ofonly 3.1±1.2% (P<0.0001 v. dose 1) 20 minute post-drug and 2.2±1.0%(P<0.0001 v. dose 1) at 30 minutes post-drug. Maximal tolerance tomorphine developed at 5 days of b.i.d dosing.

Tolerance to DPI-125:

FIG. 2 shows the MPE antinociceptive response to 2.0 mg/kg/day (1.0mg/kg/dose) DPI-125 over repeated doses/days at both the 20 and 30minute post-drug time points. Repeated measures analysis of varianceindicated that there was a significant difference between the toleranceprofile of the antinociceptive action of repeated DPI-125 dosing(P<0.0001). Further analysis with pair wise Student's t-testsdemonstrated a significant difference between the antinociceptiveeffects of DPI-125 recorded 20 minutes and 30 minutes after the 5th dose(the first dose of day 3; MPE 84.7±10.0% at 20 minutes and 66.7±10.9% at30 minutes post-drug; P<0.05), the 9th dose (the first dose of day 5;MPE 75.9±9.5% at 20 minutes and 40.8±11.2% at 30 minutes post-drug;P<0.05) and the 10th dose (the second dose of day 5; MPE 47.4±11.9% at20 minutes and 28.5±9.3% at 30 minutes) of DPI-125.

Tolerance to Antinociceptive Action Measured 20 Minutes Post-Drug:

When the antinociceptive activity of DPI-125 was measured 20 minutespost-drug, significant tolerance developed by the first dose of day 4(MPE 70.6±12.3%; P<0.05 v. dose 1) and was present at the 10th, 11th and12th doses (dose 2 of day 5 and doses 1 and 2 of day 6: MPE 47.4±11.9%,34.2±12.5%, 37.7±12.7% respectively; P<0.0001 v. dose 1). Maximumtolerance (0% MPE) was not present by the end of 6 days of dosing (afterthe 12th dose), although the two doses on day 6 produced MPE of34.2±12.5% and 37.7±12.7% respectively. During the DPI-125 challengedosing period (days 7 and 8), however, the MPE did reach as low as1.8±1.8% (the second dose of day 8). Complete tolerance to DPI-125developed at 8 days of b.i.d. dosing.

Tolerance to Antinociceptive Action Measured 30 Minutes Post-Drug:

When the antinociceptive activity of DPI-125 was measured 30 minutesafter dosing, significant tolerance was developed by the first dose ofday 3 (MPE 66.7±10.9%; P<0.005 v. dose 1) and was present through allsubsequent doses (FIG. 2, Table 4). As with the 20 minute time point,complete tolerance was not developed after any of the 12 dosesadministered, although the last dose (second dose of day 6) produced anMPE of 11.8±7.9% which was significantly lower than the lowest MPErecorded at 20 minutes (34.2±12.5%; P<0.05).

Morphine Challenge to Morphine Tolerant Animals:

As described above, morphine tolerance was established through twicedaily subcutaneous dosing of 5.0 mg/kg morphine sulfate for 5 days.Morphine sulfate was administered in a similar manner on days 6, 7, and8. The antinociceptive effects of the morphine sulfate challenge dosesare presented in FIG. 1. Challenge doses of morphine sulfate producedsignificantly less antinociception than the first dose on day 1(P<0.0001 for all comparisons) but there was no significant differencebetween the antinociception produced by any challenge dose and the lastdose of the 5 days of tolerance development (P>0.05 for all comparisons:Table 3). This persistent tolerance to morphine sulfate was evident atboth the 20 and 30 minute test time-points.

Morphine Challenge to DPI-125 Tolerant Animals:

Following the establishment of tolerance to the antinociceptive effectsof DPI-125 (1.0 mg/kg) over 6 days of dosing, twice daily challengedoses of morphine (5.0 mg/kg) produced significantly lessantinociception than the first day of DPI-125 dosing (at both the 20 and30 minutes time points (P<0.0001 for all comparisons between days 7 and8 and day 1 dose 1). Further to this, there was no significantdifference between the antinociception produced by the final dose ofDPI-125 used to establish antinociceptive tolerance and any of themorphine challenge doses either 20 or 30 minutes post-drug (P>0.05 forall comparisons; Table 3). There was no significant difference betweenthe antinociception produced by morphine sulfate (5.0 mg/kg) doses aftertolerance had been established to either morphine sulfate (5.0 mg/kg) orDPI-125 (1.0 mg/kg) (P>0.05 for Student's t-test comparisons betweenparallel test days).

DPI-125 Challenge to DPI-125 Tolerant Animals:

DPI-125 tolerance was induced through twice daily doses of 1.0 mg/kg for6 days at which point the antinociceptive MPE was 37.7±12.7% 20 minutespost-drug and 11.8±7.9% 30 minutes post-drug. Despite the lack ofinduction of complete tolerance (0% MPE) to DPI-125, challenge doses of1.0 mg/kg twice daily for 2 days produced significantly lessantinociception than the first dose of the tolerance schedule (P<0.0001for all comparison at both 20 and 30 minute antinociceptiveassessments). At the 20 minute antinociceptive assessment there weresignificantly attenuated antinociceptive responses to all challengedoses tested when compared with the effect of the last tolerance dose(P<0.05 for all comparisons; Table 4). However, at the 30 minutepost-drug test time point there was no significant difference betweenthe antinociceptive effects of any challenge dose relative to the lastdose of the tolerance schedule (P>0.05; FIG. 2).

DPI-125 Challenge to Morphine Tolerant Animals:

Following the establishment of tolerance to the antinociceptive effectsof morphine sulfate (as described above), twice daily challenge doses ofDPI-125 (1.0 mg/kg) produced significantly less antinociception than thefirst tolerance dose at all challenge doses (P<0.0001; Table 4) exceptthe second dose on the first challenge day (day 6) when antinociceptionwas recorded 20 minutes post-drug (P>0.05). However, whenantinociception was recorded 30 minutes post-drug, all challenge dosesproduced significantly less antinociception than the first tolerancedose (P<0.0001; Table 4) except for the first challenge dose (day 6 dose1; P>0.05). More critically, however, DPI-125 challenge to morphinetolerant animals produced clearly and significantly higher levels ofantinociception than the last tolerance doses of morphine, or than themorphine challenge doses (P<0.0005; FIG. 2). This antinociceptiveefficacy of DPI-125 challenge doses was evident for the first 4challenge doses at the 20 minute post-drug test time point but just thefirst 3 challenge doses when antinociceptive testing was carried out 30minutes post-drug. The maximum level of antinociception produced by anysingle DPI-125 challenge dose (MPE 81.6±12.6% at 20 minutes and80.7±15.2% at 30 minutes) was approximately equivalent to the effect ofthe same DPI-125 dosing after 6 repeated doses in naïve animals whenmeasured at the 20 minute time point and after 5 repeated doses whenmeasured at the 30 minute time point.

Study 2:

The effect of tolerance to DPI-125 or morphine sulfate on theantinociceptive potency of morphine sulfate. FIG. 3 and Table 5 show thedose response curve and ED50 values for morphine sulfate administeredsubcutaneously to rats that were either naïve to morphine sulfate,tolerant to morphine sulfate or tolerant to DPI-125. The data presentedshows the effect of morphine sulfate administration, R² values for thecurve fit ranged were all 0.83 or higher. When administered to naïveanimals, morphine sulfate produced antinociception with a mean ED50value of 2.04^((1.5-2.84)) mg/kg. The potency of morphine sulfate wasgreatly reduced (by 5.5 fold) when administered to animals tolerant tomorphine sulfate. In this case the ED50 value was 11.26^((8.1-15.6))mg/kg. The administration of morphine sulfate to animals tolerant toDPI-125 showed an even greater reduction in antinociceptive potency ofmorphine sulfate (7.8 fold) with an ED50 value of 15.82^((13.25-18.9))mg/kg.

Study 3:

The effect of tolerance to DPI-125 or morphine sulfate on theantinociceptive potency of DPI-125. FIG. 4 and Table 5 show the doseresponse curve and ED50 values for DPI-125 administered subcutaneouslyto rats that were either naïve to DPI-125, tolerant to DPI-125 ortolerant to morphine sulfate. The data presented shows the effect ofDPI125 administration, R2 values for the curve fit were 0.95 and higher.When administered to naïve animals, DPI-125 produced antinociceptionwith an ED50 value of 0.41^((0.27-0.63)) mg/kg. Following thedevelopment of tolerance to DPI-125, however, there was a 2.99 folddecrease in antinociceptive potency with an ED50 value of1.22^((121-1.23)) mg/kg. The antinociceptive potency of DPI-125 was alsoaffected by the induction of tolerance to morphine sulfate. In theseanimals, DPI-125 was 1.7 fold more potent than in those animals tolerantto DPI-125. However, DPI-125 was 1.8 fold more potent in animals naïveto DPI-125 than those tolerant to morphine sulfate. The ED50 value forantinociception in animals that were tolerant to morphine was0.72^((0.67-0.77)) mg/kg.

The results presented here from Study 1 demonstrate that both morphinesulfate (10.0 mg/kg/day) and DPI-125 (2.0 mg/kg/day) produce toleranceto their antinociceptive effects. However, DPI-125 tolerance was slowerin onset and rate than morphine sulfate such that maximal loss ofantinociception occurred with morphine sulfate after approximately halfas many doses as with DPI-125. Further to this, morphine sulfate had noantinociceptive effects in animals tolerant to either morphine sulfateor DPI-125. Likewise, DPI-125 had no antinociceptive effects in animalstolerant to DPI-125, but there were significant antinociceptive effectsof DPI-125 in animals tolerant to morphine sulfate. Studies 2 and 3indicate that DPI-125 shows a smaller loss in antinociceptive potency inanimals tolerant to morphine sulfate (1.7 fold) or DPI-125 (2.99 fold)than was seen with morphine in animals tolerant to morphine (5.5 fold)or DPI-125 (7.8 fold).

In Conclusion:

Morphine sulfate and DPI-125 produce antinociceptive tolerance followingtwice daily subcutaneous doses of 5.0 mg/kg and 1.0 mg/kg respectively.The rate of tolerance development also differed. Maximal tolerance wasreached at 5 and 8 days respectively. There was appreciable crosstolerance between morphine sulfate and DPI-125 at these doses, althoughDPI-125 remained active in animals completely tolerant to morphinesulfate. DPI-125 tolerance produced a 2.99 fold shift in theantinociceptive ED50 of DPI-125. Morphine sulfate tolerance produced a5.5 fold shift in the antinociceptive ED50 of DPI-125.

References; The contents of all references cited herein are incorporatedby reference herein for all purposes.

-   1. Sellers E M, Perrino P J, Colucci S V, Harris S C: Attractiveness    of reformulated OxyContin® tablets: assessing comparative    preferences and tampering potential. J Psychopharmacol 2013,    27:808-816.-   2. Kisak E, Buyuktimkin N, Buyuktimkin S, Newsam J, Wen J, Shudo J,    Jain A: Compositions and methods for transdermal delivery of    hormones and other medicinal agents. U.S. Pat. No. 9,144,553, 2015.-   3. Van Buskirk G A, Arsulowicz D, Basu P, Block L, Cai B, Cleary G    W, Ghosh T, Gonzalez M A, Kanios D, Marques M, Noonan P K, Ocheltree    T, Schwarz P, Shah V, Spencer T S, Tavares L, Ulman K, Uppoor R,    Yeoh T: Passive transdermal systems whitepaper incorporating current    chemistry, manufacturing and controls (CMC) development principles.    AAPS PharmSciTech 2012, 13:218-230.-   4. Kisak E T, Newsam J M, King-Smith D, Karande P, Mitragotri S:    Topical formulation including diclofenac, or a pharmaceutically    acceptable salt thereof. U.S. Pat. No. 7,795,309, 2010.-   5. Kisak E T, Newsam J M, King-Smith D, Karande P, Mitragotri S:    Topical formulation. U.S. Pat. No. 8,343,962, 2013.-   6. Hammond F H: In Handbook of Pressure Sensitive Adhesive    Technology, 2nd ed. Edited by Satas D: Van Nostrand Reinhold:38-60.-   7. Inturrisi C E: Opioid analgesic therapy in cancer pain. In    Advances in Pain Research and Therapy. Vol. 16. Edited by Foley K M:    Raven Press; 1990:133-154.-   8. Clotz M A, Nahata M C: Clinical uses of fentanyl, sufentanil, and    alfentanil. Clin Pharm 1991, 10:581-593.-   9. Holder K A, Dougherty T B, Porche V H, Chiang J S: Postoperative    pain management. Int Anesthesiol Clin 1998, 36:71-86.-   10. Gutstein H B, Akil H: Opioid analgesic. In Goodman and Gilman's    The Pharmacological Basis of Therapeutics. 10th Edition. Edited by    Gilman A G, Hardman J G, Limbird L E: McGraw-Hill Companies;    2001:569-619.-   11. O'Neill S J, Collins M A, Pettit H O, McNutt R W, Chang K J:    Antagonistic modulation between the delta opioid agonist BW373U86    and the mu opioid agonist fentanyl in mice. J Pharmacol Exp Ther    1997, 282:271-277.-   12. Su Y F, McNutt R W, Chang K J: Delta-opioid ligands reverse    alfentanil-induced respiratory depression but not antinociception. J    Pharmacol Exp Ther 1998, 287:815-823.-   13. Funada M, Suzuki T, Narita M, Misawa M, Nagase H (1993).    Blockade of morphine reward through the activation of kappa-opioid    receptors in mice. Neuropharmacol 32: 1315-1323.-   14. Xi Z X, Fuller S A, Stein E A (1998). Dopamine release in the    nucleus accumbens during heroin self-administration is modulated by    kappa opioid receptors: an in vivo fast-cyclic voltammetry study. J    Pharmacol Exp Ther 284: 151-161.-   15. Bowen C A, Negus S S, Zong R, Neumeyer J L, Bidlack J M, Mello N    K (2003). Effects of mixed-action kappa/mu opioids on cocaine    self-administration and cocaine discrimination by rhesus monkeys.    Neuropsychopharmacol 28: 1125-1139.-   16. Negus S S, Schrode K, Stevenson G W (2008). Mu/kappa opioid    interactions in rhesus monkeys: implications for analgesia and abuse    liability. Exp Clin Psychopharmacol 16: 386-399.-   17. Pan Z Z (1998). mu-Opposing actions of the kappa-opioid    receptor. Trends Pharmacol Sci 19: 94-98.-   18. Wang Y H, Sun J F, Tao Y M, Chi Z Q, Liu J G (2010). The role of    kappa-opioid receptor activation in mediating antinociception and    addiction. Acta Pharmacol Sin 31: 1065-1070.-   19. Xi Z X, Fuller S A, Stein E A (1998). Dopamine release in the    nucleus accumbens during heroin self-administration is modulated by    kappa opioid receptors: an in vivo fast-cyclic voltammetry study. J    Pharmacol Exp Ther 284: 151-161.-   20. Gengo P J, Pettit H O, O'Neill S J, Wei K, McNutt R, Bishop M J,    Chang K J: DPI-3290    [(+)-3-((alpha-R)-alpha-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-hydroxybenzyl)-N-(3-fluorophenyl)-N-methylbenzamide]. I.    A mixed opioid agonist with potent antinociceptive activity. J    Pharmacol Exp Ther 2003, 307:1221-1226.-   21. Gengo P J, Pettit H O, O'Neill S J, Su Y F, McNutt R, Chang K J:    DPI-3290    [(+)-3-((alpha-R)-alpha-((2S,5R)-4-Allyl-2,5-dimethyl-1-piperazinyl)-3-hydroxybenzyl)-N-(3-fluorophenyl)-N-methylbenzamide]. II.    A mixed opioid agonist with potent antinociceptive activity and    limited effects on respiratory function. J Pharmacol Exp Ther 2003,    307:1227-1233.-   22. Gengo P J, Chang K-W: Mixed opioid receptor agonists as a new    class of agents for the treatment of moderate to severe pain. I. In    The Delta Receptor. Edited by Chang K-J, Porreca F, Woods J H:    Marcel Dekker; 2004:231-244.-   23. Brito R, Sheth S, Mukherjea D, Rybak L P and Ramkumar V (2014)    TRPV1: A Potential Drug Target for Treating Various Diseases. Cells    3:517-545.-   24. Eisenach J C, Curry R, Tong C, Houle T T and Yaksh T L (2010)    Effects of intrathecal ketorolac on human experimental pain.    Anesthesiology 112:1216-1224.-   25. Lazar J, Gharat L, Khairathkar-Joshi N, Blumberg P M and    Szallasi A (2009) Screening TRPV1 antagonists for the treatment of    pain: lessons learned over a decade. Expert Opin Drug Discov    4:159-180.-   26. Ding H, Czoty P W, Kiguchi N, Cami-Kobeci G, Sukhtankar D D,    Nader M A, Husbands S M and Ko M C (2016) A novel orvinol analog,    BU08028, as a safe opioid analgesic without abuse liability in    primates. Proc Natl Acad Sci USA 113:E5511-5518.-   27. Hu E, Calo G, Guerrini R and Ko M C (2010) Long-lasting    antinociceptive spinal effects in primates of the novel    nociceptin/orphanin F Q receptor agonist UFP-112. Pain 148:107-113.-   28. Ko M C, Terner J, Hursh S, Woods J H and Winger G (2002)    Relative reinforcing effects of three opioids with different    durations of action. J Pharmacol Exp Ther 301:698-704.-   29. Ding H, Hayashida K, Suto T, Sukhtankar D D, Kimura M,    Mendenhall V and Ko M C (2015) Supraspinal actions of    nociceptin/orphanin F Q, morphine and substance P in regulating pain    and itch in non-human primates. Br J Pharmacol 172:3302-3312.-   30. Ko M C and Naughton N N (2009) Antinociceptive effects of    nociceptin/orphanin FQ administered intrathecally in monkeys. J Pain    10:509-516.-   31. Lee H and Ko M C (2015) Distinct functions of opioid-related    peptides and gastrin-releasing peptide in regulating itch and pain    in the spinal cord of primates. Sci Rep 5:11676.-   32. Richardson N R and Roberts D C (1996) Progressive ratio    schedules in drug self-administration studies in rats: a method to    evaluate reinforcing efficacy. Journal of neuroscience methods    66:1-11.-   33. Rowlett J K (2000) A labor-supply analysis of cocaine    self-administration under progressive-ratio schedules: antecedents,    methodologies, and perspectives. Psychopharmacology (Berl) 153:1-16.-   34. Lavonas E J, Severtson S G, Martinez E M, Bucher-Bartelson B, Le    Lait M C, Green J L, Murrelle L E, Cicero T J, Kurtz S P, Rosenblum    A, Surratt H L and Dart R C (2014) Abuse and diversion of    buprenorphine sublingual tablets and film. Journal of substance    abuse treatment 47:27-34.-   35. Cheng Y and Prusoff W H (1973) Relationship between the    inhibition constant (K1) and the concentration of inhibitor which    causes 50 percent inhibition (I50) of an enzymatic reaction. Biochem    Pharm 22:3099-3108.

TABLE 1 The Dosing Groups for Study 2 Group No. of Total Daily Dose DoseVolume Concentration No. 1.1.1.1.1. Test Article (mg/kg/day) (mg/kg BID)(ml/kg) (mg/ml) 1 6 Control Days 1 to 6 - 0 0.0 1.0 0.0 Morphine Day 7 -1.0 0.5 1.0 0.5 Sulfate 2 6 Control Days 1 to 6 - 0 0.0 1.0 0.0 MorphineDay 7 - 2.0 1.0 1.0 1.0 Sulfate 3 6 Control Days 1 to 6 - 0 0.0 1.0 0.0Morphine Day 7 -5.0 2.5 1.0 2.5 Sulfate 4 6 Morphine Days 1 to 6 - 10.05.0 1.0 5.0 Sulfate Morphine Day 7 - 15.0 7.5 1.0 7.5 Sulfate 5 6Morphine Days 1 to 6 - 10.0 5.0 1.0 5.0 Sulfate Morphine Day 7 - 20.010.0 1.0 10.0 Sulfate 6 6 Morphine Days 1 to 6 - 10.0 5.0 1.0 5.0Sulfate Morphine Day 7 - 25.0 12.5 1.0 12.5 Sulfate 7 6 Morphine Days 1to 6 - 10.0 5.0 1.0 5.0 Sulfate Morphine Day 7 - 30.0 15.0 1.0 15.0Sulfate 8 6 Morphine Days 1 to 6 - 10.0 5.0 1.0 5.0 Sulfate DPI-125 Day7 - 0.5 0.25 1.0 0.25 9 6 Morphine Davs 1 to 6 - 10.0 5.0 1.0 5.0Sulfate DPI-125 Day 6 - 1.0 0.5 1.0 0.5 10 6 Morphine Days 1 to 5 - 10.05.0 1.0 5.0 Sulfate DPI-125 Day 7 - 2.0 1.0 1.0 1.0 11 6 Morphine Davs 1to 6 - 10.0 5.0 1.0 5.0 Sulfate DPI-125 Day 7 - 3.0 1.5 1.0 1.5

TABLE 2 Dosing Groups for Study 3 Group No. of Dose Volume ConcentrationNo. Rats Test Article Total Daily Dose (mg/kg BID) (ml/kg) (mg/ml) 12 6Control Days 1 to 6 - 0 0.0 1.0 0.0 DPI-125 (D) Day 7 - 0.25 0.125 1.00.125 13 6 Control Days 1 to 6 - 0 0.0 1.0 0.0 DPI-125 (D) Day 7 - 0.500.25 1.0 0.25 14 6 Control Days 1 to 6 - 0 0.0 1.0 0.0 DPI-125 (D) Day7 - 1.0 0.5 1.0 0.5 15 6 DPI-125 (D) Days 1 to 6 - 2.0 1.0 1.0 1.0DPI-125 (D) Day 7 - 2.25 1.125 1.0 1.125 16 6 DPI-125 (D) Days 1 to 6 -2.0 1.0 1.0 1.0 DPI-125 (D) Day 7 - 2.5 1.25 1.0 1.25 17 6 DPI-125 (D)Days 1 to 6 - 2.0 1.0 1.0 1.0 DPI-125 (D) Day 7 - 3.0 1.5 1.0 1.5 18 6DPI-125 (D) Davs 1 to 6 - 2.0 1.0 1.0 1.0 DPI-125 (D) Day 7 - 3/5 1.751.0 1.75 19 6 DPI-125 (D) Days 1 to 6 - 2.0 1.0 1.0 1.0 Morphine Day 7 -20.0 10.0 1.0 10.0 Sulfate 20 6 DPI-125 (D) Days 1 to 6 - 2.0 1.0 1.01.0 Morphine Day 7 - 30.0 15.0 1.0 15.0 Sulfate 21 6 DPI-125 (D) Days 1to 6 - 2.0 1.0 1.0 1.0 Morphine Day 7 - 40.0 20.0 1.0 20.0 Sulfate 22 6DPI-125 (D) Days 1 to 6 - 2.0 1.0 1.0 1.0 Morphine Day 7 - 50.0 25.0 1.025.0 Sulfate

TABLE 3 The Antinociceptive Effects of Repeated Morphine DosesDevelopment of Morphine Tolerance Day 1 1.25 2 2.25 3 3.25 4 4.25 5 5.25Dose 1 2 3 4 5 6 7 8 9 10 20 minutes Post-drug Mean MPE 100.0 100.0 78.956.6 33.8 32.9 23.7 7.0 3.1 5.3 s.e.m. 0.0 0.0 8.2 10.8 8.9 8.9 7.3 2.91.3 1.5 30 minutes Post Drug Mean MPE 100.0 100.0 75.9 57.9 46.5 24.120.6 5.7 2.2 3.9 s.e.m. 0.0 0.0 9.0 7.8 9.4 7.5 8.5 1.8 1.1 1.0Challenge Doses to Morphine Tolerant Day 6 6.25 7 7.25 6 6.25 7 7.25Challenge Dose 1 2 3 4 1 2 3 4 Morphine Challenge (20 min) DPI-125Challenge (20 min) Mean MPE 4.4 0.9 0.0 2.6 Mean MPE 64.9 81.6 50.9 30.7s.e.m. 1.8 1.0 0.0 1.3 s.e.m. 13.9 13.8 13.3 16.7 Morphine Challenge (30min) DPI-125 Challenge (30 min) Mean MPE 4.4 2.6 0.9 1.8 Mean MPE 80.742.1 57.0 26.3 s.e.m. 1.8 1.3 1.0 1.2 s.e.m. 16.7 20.4 19.9 17.6

TABLE 4 The Antinociceptive Effects of Repeated DPI-125 DosesDevelopment of DPI-125 Tolerance Day 1 1.25 2 2.25 3 3.25 4 4.25 5 5.256 6.25 Dose 1 2 3 4 5 6 7 8 9 10 11 12 20 minutes Post-drug Mean MPE100.0 100.0 99.1 79.8 84.7 81.1 70.6 75.0 75.9 47.4 34.2 37.7 s.e.m. 0.00.0 0.9 7.9 10.4 9.2 12.9 10.6 9.9 12.4 13.0 13.3 30 minutes Post DrugMean MPE 100.0 100.0 100.0 88.2 66.7 69.7 72.8 51.3 40.8 28.5 21.1 11.8s.e.m. 0.0 0.0 0.0 5.1 11.4 11.8 11.1 9.3 11.7 9.7 8.0 8.3 ChallengeDoses to DPI-125 Tolerant Day 7 7.25 8 8.25 7 7.23 8 8.25 Challenge Dose1 2 3 4 1 2 3 4 Morphine Challenge (20 min) DPI-125 Challenge (20 min)Mean MPE 1.76 0.00 3.51 0.88 Mean MPE 8.77 22.82 9.65 1.76 s.e.m. 1.920.00 1.21 0.96 s.e.m. 3.22 6.78 3.13 1.92 Morphine Challenge (30 min)DPI-125 Challenge (30 min) MeanMPE 2.63 1.75 0.00 0.00 Mean MPE 3.517.90 2.63 0.88 s.e.m. 1.29 1.21 0.00 0.00 s.e.m. 1.92 2.88 2.88 0.96

TABLE 5 Antinociceptive Effects of Repeated Morphine and DPI-125 dosing(Studies 2 & 3) Confidence Drug Treatment ED₅₀ Interval R² Fold ChangeMorphine to naive animals 2.037 1.509-2.750 0.98 Morphine to morphine11.26 8.115-15.64 0.83 5.5 tolerant animals Morphine to DPI-125 15.8213.25-18.90 0.98 7.8 tolerant animals DPI-125 to naïve animals 0.4070.265-0.625 0.95 DPI-125 to DPI-125 1.218 1.211-1.226 0.99 3.0 tolerantanimals DPI-125 to morphine 0.717 0.671-0.766 0.99 1.8 tolerant animals

1. A method of preventing, reducing and/or treating drug addictionwherein the method comprises administering to a subject a compoundhaving the structure of formula (I):

having the IUPAC name of(−)3-((S)-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)(3-thienyl)methyl)phenol,or pharmaceutically acceptable esters or salts thereof, wherein thecompound has activity on the mu, delta and kappa opioid receptorsthereby providing added analgesia with an improved therapeutic index andreduced risk of respiratory depression thereby resulting in reducedabuse potential compared to standard mu opiate agonists.
 2. The methodof claim 1, further comprising the ability to reduce the euphoriceffects associated with mu receptor activation,
 3. (canceled)
 4. Apharmaceutical composition comprising: (a) an effective amount of abioactive agent for treatment of a condition selected from the groupconsisting of drug addiction or drug overdose; and (b) an effectiveamount of a compound comprising the formula:

(−)3-((S)-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)(3-thienyl)methyl)phenolor a pharmaceutically acceptable salt or esters thereof.
 5. A method totreat drug addiction by administering a compound having the structure offormula (I):

having the IUPAC name of(−)3-((S)-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)(3-thienyl)methyl)phenol,or pharmaceutically acceptable esters or salts thereof.
 6. The method ofclaim 5, wherein the drug addiction is related to consumption of ancocaine, heroin, opium, amphetamine, or methamphetamine.
 7. The methodof claim 5, wherein the compound of formula (I) is combined withmethadone. 8.-11. (canceled)
 12. The pharmaceutical composition of claim4, wherein the bioactive agent is methadone.